The number of times I’ve heard someone say “Ooh, my knees are cracking – I’m getting old!” yet soon after someone else is saying “The chiro cracked my back today and now I feel amazing” – so which is it? A tell-tale sign of your age or worth $100 for a bit of relief?

First thing’s first. The noise.

Nobody really knows what causes the noise. At uni I was taught it’s a cavitation process; the gapping of a joint results in a drop in pressure within the joint, allowing gas from the surrounding synovial fluid to enter the space forming a ‘bubble’. The closing down of this joint causes the air bubble to ‘burst’, making the cracking sound(1). (Yes, an explanation based on an article published in 1995 – go uni).  

Great! I love a succinct explanation.

Is it true? Who knows.

But now let’s discuss what really matters;

Is it therapeutic or concerning?

A good rule of thumb is, if it’s painful, it swells up – get it looked at. It could be nothing, but if it’s stopping you from doing what you love then that’s something a (good!) physio can help you with. If it’s not, crack away (I write this cringing – I hate knuckle cracking!). There is no evidence correlating joint cracking and osteoarthritis – and that one causes the other(2). Otherwise chiro’s would be out of a job.

To support my point, a 2018 study by M.F. Pazzinatto et al investigated the effect of crepitus in a population of individuals with knee osteoarthritis. It had no significant impact on knee strength and function(3). What should be considered however, is the impact that the sound has on the individual’s perception of how they use their body and that there is a potential for them to develop fear-avoidance behaviours. When their response is not to move, that’s when it becomes a problem. So make sure you do the opposite! Keep your strength up even if your joints erupt into a symphony of crackles. Believe me, I can relate.

The relief that people experience has a lot to do with the patient-therapist interaction, manual handling and the satisfaction of an ‘outcome’ i.e. the ‘crack’.

There is a lack of understanding as to what is happening within the joint as well as the surrounding structures. There’s talk of overriding reflexes causing the surrounding ligaments and muscles to relax – but at this point it’s all hypotheses and guess-work with evidence lacking to support these claims(4). In the end, it doesn’t matter because it’s the experience and what you value that counts. This is what therapists who use this form of manual therapy harness to keep you coming back for more.

So keep debunking the myth in front of your friends that cracking leads to arthritis and don’t let it stop you from doing what your body does best – moving!

References:

1. Brodeur R. The audible release associated with joint manipulation. Journal of Manipulative and Physiological Therapeutics. 1995, 18(3):155-164.
2. Protopapas MG, Cymet TC. Joint cracking and popping: understanding noises that accompany articular release. The Journal of the American Osteopath Association. May 2002, Vol. 102, 283-287.
3. Pazzinatto et al. What are the clinical implications of knee crepitus to individuals with knee osteoarthritis? An observational study with data from the Osteoarthritis Initiative. Braz J Phys Ther. Nov 2018. pii: S1413-3555(18)30240-5
4. Kawchuk GN, Fryer J, Jaremko JL, Zeng H, Rowe L, Thompson R. Real-Time Visualization of Joint Cavitation. PLOS ONE. Apr 2015. 10(4): e0119470.